Pantex employees ready a mock warhead for testing as part of efforts to ensure the nation's nuclear arsenal stands ready. The Pantex Plant constructed the warhead used in a May test launch of the Minuteman III intercontinental ballistic missile. IPad users, click on the photo to view more photos from this article.

On May 28, an orange pillar of flames billowed out from an underground launch platform at California’s Vandenberg Air Force Base as a mock Minuteman III missile roared skyward on a 4,200-mile flight to a tiny atoll in the Central Pacific Ocean.

Tucked inside the unarmed missile, a battery of testing equipment monitored the flight’s every move, providing vital tracking and other data to government scientists.

The Minuteman III mock warhead, dubbed a W87 joint test assembly, was built at the Pantex Plant, Air Force officials said.

The successful test, the collaborative work of hundreds of scientists, engineers and military personnel, began, in part, at Pantex, a Carson County plant where the nation’s nuclear weapons are dismantled or modified.

At Pantex, a team of about 50 to 60 employees builds mock warheads to meet rigorous standards set by nation’s nuclear weapons laboratories, said Program Manager Colby Yeary.

“Basically, once the parent unit, the actual War Reserve product, is identified by the labs, it’s brought here to the plant. We do a disassembly and inspection of the unit. During that disassembly and inspection, certain parts are harvested to go into JTAs,” he said. “After that, we actually do our build with telemetries and whatever components to make it as close as possible to what the actual weapon is without being able to produce a nuclear yield.”

Each year, the National Nuclear Security Administration must certify to the president that the U.S. nuclear stockpile is safe and reliable. The joint test assembly program plays a pivotal role in that annual certification, Yeary said.

Pantex, he said, works closely with the Defense Department to ensure that test assemblies fulfill stringent military specifications and lab design procedures.

“For us, those come via requirements from the national laboratories, Los Alamos, Livermore and Sandia national laboratories,” he said. “It’s based on what the characteristics the laboratories are trying to surveil or understand or analyze.”

The U.S. arsenal has eight different types of nuclear weapons, ranging from cruise missiles to intercontinental ballistic missiles like as the Minuteman III, a 60-foot long rocket capable of carrying multiple warheads. At different times, joint test assemblies have been built for each weapon in the U.S. nuclear stockpile, officials said.

“Its just a way that they can validate that the safety and security of the weapons stockpile and the reliability of the weapons stockpile is still good,” Yeary said. “The same level of qualification and rigor is applied to a JTA as it would be for an active stockpile assembly ... The product is not so much the assembly, it’s really the data we generate from the flight test itself.”

Production Manager Curtis Chamberlain, who served in the Air Force, said he once traveled to an undisclosed location and witnessed a Minuteman III JTA launch.

“Being there, it was pretty neat. We did get a tour of the facility,” he said. “I was able to see the missile going up and the contrail afterwards.”

Kathryn Blais, an Air Force spokesman, said a typical Minuteman III test launch costs about $21 million and requires about 250 personnel, including members of the 576th Flight Test Squadron, which serves as Air Force Space Command’s experts on missile systems capabilities.

“The overall purpose of the ICBM test launch program is to validate and verify the effectiveness, readiness and accuracy of the weapon system. We have several other tests by which we obtain the data necessary to confirm the operational readiness of the ICBM fleet,” she said.

But not all test launches go as planned.

In 1999, two mock B-61 test bombs were destroyed after Pantex technicians installed dead batteries their parachute assemblies, and they plummeted to the ground, damaging more than $170,000 worth of reusable parts during “hard landings,” a government report said.

In 2011, Air Force officials destroyed a Minuteman III in flight after a launch from the Vandenberg base and another 1998 Minuteman test was terminated by mission controllers after an “anomaly” developed during the flight’s final phase, according to information from the Air Force.

Overall, the Minuteman III testing program has completed at least 26 successful launches.

At Pantex, hundreds of workers play supporting roles in the program, from crafts department personnel who build special tooling to engineers who oversee the detailed work. Pantex, he said, also works closely with other weapons sites in Kansas City, Tennessee and South Carolina on various aspects of the test assembly program.

Chamberlain said the program is a unique one that offers challenging and rewarding job vital to the nation’s defense.

“For me personally, it’s a great honor,” he said. “This is the primary place where we get to do this kind of work—not many people get to do that.”